Display devices may utilize various technologies for displaying images, such as cathode ray tube (CRT) technologies, projection-based technologies, liquid crystal display (LCD)—based technologies, etc. Some display devices may be interactive display devices which are also configured to detect touches of physical objects on a surface of the display, using technologies such as capacitive detection, resistive detection, surface acoustic wave detection, optical detection, etc. In some examples, optical detection technologies may be further configured to detect “near-touches” of physical objects located near a surface of the display.
As an example, two cameras pointing in the same direction but separated by a known distance may be used to capture two images of an object near the surface from different points of view. The two images may then be processed to reveal parallax data about the object which is related to depth. Very careful calibration is required, however, to ensure that the two cameras are effectively pointing in the same direction.